| Abstract: | 1. Macrophyte and macroinvertebrate species richness, and the extent of aquatic vegetation, were surveyed in 51 newly created or renovated ponds in mid and west Wales, together with a range of environmental variables. These data are analysed in relation to management issues including pond size, rate of development, planting for oxygenation, stocking with fish and shading by riparian trees. 2. Richness of both plants and invertebrates increases with vegetated area, but the relationships are weak. Similarities among assemblages in ponds are low and not related to the proximity of the ponds. It is likely that two small ponds would together support more species than a single large pond. 3. New ponds are colonized rapidly by plants and invertebrates. There is no relationship between age and the number of species in ponds that were at least one year old, except for invertebrates in ponds that were isolated from other wetland. As expected, the extent of aquatic vegetation increases with age. 4. Minimum dissolved oxygen levels decrease with the cover of floating plants and with extent of vegetation in relation to pond size. 5. There is no evidence that stocking with fish (mainly salmonids at low densities) influences the total number of species of either macrophytes or macroinvertebrates. However, the number of anisopteran (Insecta: Odonata) species is lower in stocked ponds and the number of trichopteran (Insecta) species is higher. 6. Macrophyte species richness increases with the percentage of the margin shaded by trees to a peak between 22% (emergent species) and 30% (submerged and floating species), and then declines. The number of species of invertebrates with short-lived flying adults (Odonata, Ephemeroptera, Trichoptera) decreases with the extent of riparian trees. Other invertebrates are unaffected. 7. The relationship between the survey results and existing management recommendations is discussed, emphasizing the need for field experiments to provide empirical support. © 1997 John Wiley & Sons, Ltd. |
